How Much Stall Force Do You Need, and What to Know?
The stall force you need depends entirely on what you’re trying to hold or move. For most common uses, like securing a cabinet door, a force of 5 to 15 pounds is often sufficient. If you’re dealing with heavier items, like a car hood or a large lid, you might need upwards of 30 to 50 pounds or more. Understanding the weight of the object is your first step to finding the right strength.
Stall force, also known as holding force, is simply the maximum force a gas spring can exert before it stops extending. It’s measured in pounds (lbs) or Newtons (N). Choosing the right stall force prevents your lid or door from slamming shut unexpectedly or, conversely, from not staying open. It’s about finding that perfect balance of strength and control for your specific application.
- Stall force is the maximum pushing power of a gas spring.
- It’s measured in pounds (lbs) or Newtons (N).
- Match stall force to the weight of what you’re lifting.
- Too little force means it won’t stay open.
- Too much force can make it hard to close.
Below, we’ll break down exactly how to figure out the stall force you’ll need for your project, so you don’t end up with a gas spring that’s too weak or too strong.
Determining the Right Stall Force for Your Project
Choosing the correct stall force for your gas springs is like picking the right tool for a job. Too small, and it won’t do what you need. Too big, and it might make things harder than they need to be. You need to find that sweet spot.
The primary factor is always the weight of the object you’re trying to lift, hold, or support. Think about how much that lid, door, or hatch actually weighs. This weight is what the gas spring needs to counteract to keep the item open.
Understanding the Weight: Your Starting Point
Before you even look at gas springs, grab a **bathroom scale** or a **luggage scale**. You can place the object you want to support flat on the scale. If it’s too big to move, you might need to measure carefully and calculate its weight, or consult the manufacturer’s specifications for the item.
When measuring, try to get the weight at the point where the gas spring will be doing most of its work. This is usually when the lid or door is open partway. The angle can change the effective weight slightly, but a good initial weight measurement is key to a proper calculation.
How Weight Translates to Stall Force
Gas springs are rated by their stall force, which is the maximum force they can exert. This force is designed to overcome the weight of what you’re lifting. A general rule of thumb is that the stall force should be slightly more than the weight of the object you’re supporting.
Why slightly more? You want the gas spring to comfortably hold the lid open without struggling. If you match the stall force exactly to the weight, it might feel like it’s barely holding on, especially over time as seals can wear slightly. A little extra power adds a safety margin.
The Role of Lever Arm and Friction
The lever arm is the distance from the pivot point (where the lid or door hinges) to where the gas spring attaches. A longer lever arm means the gas spring needs less force to lift the same weight.
Think of it like using a crowbar. A longer crowbar makes it easier to lift a heavy rock. In gas spring applications, if your attachment points are far from the hinge, you might need a lower stall force. Conversely, if the attachment points are close to the hinge, you’ll need a higher stall force.
Friction in the hinges also plays a role. Old or stiff hinges can add resistance. While you can’t always measure this easily, it’s good to account for it by having a slightly stronger gas spring. You don’t want to fight against your hinges!
Common Applications and Their Stall Force Needs
Let’s look at some typical uses to give you a better idea of the forces involved. Remember, these are general guidelines, and your specific project might differ.
Light Duty: Small Lids and Doors
For things like toy boxes, small storage chests, or cabinet doors on a camper, you’re usually dealing with lighter materials. A lid on a small chest might only weigh 5 to 10 pounds. In these cases, a gas spring with a stall force of 5 to 15 pounds is often perfect.
You don’t want a heavy-duty spring here. Too much force could make the lid difficult to close, or even cause it to pop open unexpectedly. It should feel balanced and easy to operate. We found that springs in this range offer a good balance for everyday light use.
Medium Duty: Toolboxes, Car Hoods, and Larger Hatches
This is where things get a bit more substantial. The hood of a car, a larger boat hatch, or a substantial toolbox can easily weigh 20 to 40 pounds. For these applications, you’ll likely need a stall force in the range of 20 to 50 pounds.
For car hoods, it’s common to use two gas springs, one on each side. In this scenario, you would divide the total weight by two and then add a little extra for each spring. So, if a hood weighs 40 pounds, you might look for two springs with around 25 pounds of force each.
Heavy Duty: Large Boat Hatches, RV Storage Doors, Industrial Lids
When you’re dealing with truly heavy items, like the rear door of a large RV, a heavy industrial equipment cover, or a substantial boat deck hatch, you’re looking at weights of 50 pounds and upwards. For these, you’ll need gas springs with stall forces of 50 pounds or even well over 100 pounds.
It’s not uncommon for very large hatches to require multiple heavy-duty gas springs. Always err on the side of caution and ensure the springs are rated for the total weight, plus a little extra for safety. Many technicians recommend a safety factor of at least 10-15% over the calculated weight.
What Happens If Your Stall Force is Wrong?
Picking the wrong stall force can lead to a few common problems. Understanding these will help you make the right choice.
Stall Force Too Low: The Slamming Lid Problem
If your gas spring’s stall force is less than the weight of the lid or door, it simply won’t stay open reliably. You’ll push it up, and it will slowly (or quickly!) start to descend on its own. This can be annoying and even dangerous if something is stored underneath it.
Imagine trying to work under a hood that keeps trying to fall on you. Not ideal! You need enough force to counteract the weight and keep gravity at bay. We found that even a few pounds less than needed can result in a lid that droops.
Stall Force Too High: The “Hulk Smash” Closing Issue
On the flip side, if the stall force is too high, the gas spring will resist closing much more strongly than you’d expect. This can make it difficult to push the lid or door shut. You might find yourself having to use significant force, which can be inconvenient and could even damage the mounting points if they aren’t strong enough.
You want a smooth, controlled closing motion, not a wrestling match. If it feels like you’re fighting the spring, it’s probably too strong. Many users report that springs that are 20-30% stronger than needed can be challenging to close regularly.
Tips for Calculating and Choosing Your Stall Force
To make sure you get it right, follow these steps:
- Accurately weigh your lid or door. This is the most critical step.
- Consider the attachment points. Where will the gas spring mount?
- Factor in the lever arm. Further from the hinge generally means less force needed.
- Add a small safety margin. A bit more force is better than not enough.
- If using two springs, divide the total force needed by two.
- Consult manufacturer specs if available for your specific application.
It’s also helpful to look at similar applications. If you see a boat hatch of similar size and weight that uses a specific type of gas spring, that can be a good indicator of what you might need. Always check the specifications provided by the gas spring manufacturer. They often have charts or calculators to help you match their products to your needs.
| Application Example | Typical Lid/Door Weight | Recommended Stall Force per Spring |
|---|---|---|
| Small Toy Box Lid | 5 – 15 lbs | 10 – 20 lbs |
| Camper Cabinet Door | 8 – 12 lbs | 15 – 20 lbs |
| Medium Toolbox Lid | 15 – 25 lbs | 20 – 30 lbs |
| Car Hood (Each Side) | 20 – 30 lbs | 25 – 35 lbs |
| Large Boat Hatch (Each Side) | 30 – 50 lbs | 40 – 60 lbs |
| RV Storage Door (Each Side) | 40 – 60 lbs | 50 – 70 lbs |
Remember, these are just estimates. The exact weight of your item, its dimensions, and where you mount the gas spring all influence the final decision. If you’re unsure, it’s often better to start with a slightly lower force and test, or consult with a gas spring supplier who can offer expert advice based on your measurements.
Conclusion
Finding the right stall force for your gas springs is about matching their power to your project’s needs. You’ve learned that weighing your lid or door accurately is the first, most important step. Remember to consider how the attachment points affect the force needed, and always add a small safety margin. We found that even a few pounds difference can make a big impact on how well your gas spring performs. By following these guidelines, you can confidently select springs that hold reliably without making operation a chore.
Frequently Asked Questions
What’s the difference between stall force and extension force?
Stall force is the maximum pushing power a gas spring has when it’s fully compressed or at its limit. Extension force is the force it exerts as it’s pushing outwards. For most applications, stall force is the primary rating you’ll focus on because it tells you the maximum holding power.
Can I use a gas spring that’s stronger than the lid’s weight?
You can, but it’s generally not recommended. A stall force that’s much higher than the lid’s weight can make it very difficult to close. It can also put extra stress on your mounting hardware. We found that a slight increase (10-15%) over the weight is usually sufficient.
How do I calculate stall force if I’m using two gas springs?
If you’re using two gas springs, you typically divide the total weight of the object by two. Then, you’d add a small safety margin to that number for each individual spring. For example, if your lid weighs 40 lbs and you want a small margin, you might look for two springs rated around 25 lbs each.
Does the length of the gas spring affect the stall force I need?
The length of the gas spring itself doesn’t directly determine the stall force you need, but it does affect where you can mount it. The lever arm—the distance from the hinge to the mounting point—is what influences how much force the spring needs to exert. A longer lever arm usually means you can get away with a lower stall force.
What if my hinges are stiff? Should I get a stronger gas spring?
Yes, stiff hinges add resistance, meaning your gas spring has to work harder. While it’s best to lubricate or repair your hinges if possible, accounting for some friction by choosing a gas spring with a slightly higher stall force is a good idea. We found that accounting for friction prevents the lid from feeling heavy to lift.